1. Field of the Invention
The present invention relates to a technology of generating panoramic tomography X-ray images.
2. Description of the Background Art
In dental treatment, panoramic X-ray tomography is performed for checking the conditions of the teeth (dentition) and gums of patients. In this panoramic X-ray tomography, an X-ray source and an X-ray detector are caused to revolve about an object (patient) in the state of facing each other so as to sandwich a jaw portion of the object therebetween, to thereby collect pieces of X-ray transparent data (frame images) at a predetermined frame rate. Then, the computation process (shift addition) in which overlapped portions of images are superimposed along a tomographic plane corresponding to the shape of a dentition is performed, to thereby generate a panoramic tomographic image.
In order to generate a panoramic tomographic image with little blurring, it is desired to make a position of a tomographic plane correspond to the shape of the dentition as much as possible. Therefore, in Japanese Patent Application Laid-Open No. 2008-229322, the position of the dentition is specified from the image data obtained through X-ray CT tomography, and the panoramic tomographic plane is set at that position, to thereby obtain a panoramic tomographic image.
The panoramic X-ray tomography of Japanese Patent Application Laid-Open No. 2008-229322 can handle the shape of a dental arch peculiar to a patient. However, when CT imaging is performed, every portion other than the dental arch needs to be continuously irradiated with X-rays. Accordingly, from the viewpoint of the purpose to obtain a panoramic tomographic image, portions other than required need X-ray irradiation, leading to an excessive X-ray exposure.
Normally, the front teeth each extends while being inclined obliquely forward in the vicinity of the median line of the upper and lower jaws. It is, therefore, desirable to set a tomographic plane in accordance with the above-mentioned shape of the dentition, but in Japanese Patent Application Laid-Open No. 2008-229322 there is no particular description of the configuration for handling this shape.